If you're having vibration problems, balancing the prop is a first step. After that, aligning the prop with the piston, ie the prop is vertical with the piston at TDC, can help reduce vibration. If you have a slightly heavy blade, you can align it downwards with the piston at TDC to help a bit. But it's easy to over-due, and hard to get exactly right, which is why it's usually best to just balance the prop and put it on where it's convenient.

Btw, even "modern" engines are almost never "perfectly" counter-balanced internally. The crankshaft balance is always a bit smaller than it should be in theory. There are all kinds of things you can do to the innards of an engine to improve the balance and reduce vibration, but unless you're really pushing for high RPMs or you are just obsessed with vibration, you don't have to worry about it. However, it is true that the lighter Al pistons in a typical engine these days does mean less vibration than an iron piston.

Oh, as for me personally, I just slap it on there and where it is, it is. I use an electric starter, so starting isn't an issue, and frankly I don't break props, even on my gear-less combat planes. If you set it down softly enough, the prop will move out of the way of the ground and not break (works better with MAS props though).